Roadway repair is often accomplished by overlaying the existing pavement (whether of concrete or asphalt composition) with a new layer (often called a leveling course) of concrete, asphalt or other surfacing materials. Without prior surface treatment, however, this method of repair generally results in the application of insufficient quantities of paving material in the rutted, potholed or otherwise damaged areas, because the overlay will be applied at the same rate per unit of roadway width in damaged areas (which have a greater depth across the width) as in the undamaged areas. The resulting reduced density in the overlay of the previously damaged areas will lead to renewed rutting or other wear damage in the new pavement in relatively short order. However, by milling the surface of the damaged pavement, the milled surface may be rendered substantially flat so that newly added pavement will have a uniform thickness across the entire width of the roadway. In addition, a repaving technique that includes milling a thickness of old pavement and replacing it with an equivalent thickness of new pavement will return the elevation of the roadway to its initial level, whereas the placement of a leveling course atop damaged pavement will tend to raise the surface of the roadway or some portion thereof above its original elevation. This can require the raising of road shoulders, guardrails and manhole covers and the adjustment of overpass clearances, all of which are unnecessary if a proper milling technique is employed. A use of milling prior to repaving can also permit ready establishment of the proper road grade and slope, and thereby avoid drainage and safety problems. Furthermore, milling typically provides a rough surface that readily accepts and bonds with the new asphalt or other pavement overlay. Finally, milling can provide raw material that can be reclaimed for use in the production of new paving materials.
A milling machine is typically a wheeled or track-driven vehicle that is provided with a rotating drum that includes a plurality of cutting teeth. The drum is mounted in a housing on the frame of the machine and adapted to be lowered into contact with the road surface and rotated about a horizontal axis so as to cut into the surface to a desired depth as the machine is advanced along the roadway. Generally, the milling machine also includes a conveyor system that is designed to carry the majority of the milled material that has been cut from the roadway by the rotating drum to a location in front of, to the rear of or beside the machine for deposit into a truck for removal from the milling site. Sweeping machines are frequently required, however, to follow a milling machine in order to remove any milled material left behind by the milling machine prior to resurfacing.
Conventional sweeping machines typically employ a broom assembly comprising one or more brooms mounted for rotation about horizontal or vertical axes. Some conventional machines may operate by pushing the swept material to one side of the machine where it may be collected by a separate collecting device. Other conventional machines include a broom assembly and an integral assembly for collecting material swept by the broom or brooms. Such integral collecting assemblies may comprise vacuum systems for capturing the material swept by the brooms or discharge conveyors for transporting such material to a hopper or an adjacent truck. Most conventional sweeping machines having an integral collecting assembly are not enclosed or are not sufficiently enclosed to avoid leaving material on the roadway. Many such machines must make multiple passes along a roadway to clear the roadway sufficiently to allow for resurfacing.
Some sweeping machines that include integral collecting assemblies employ flexible flaps and end gates on the broom assembly in an attempt to seal the broom assembly to the roadway surface and prevent material from escaping from the broom assembly enclosure. Unfortunately, conventional flaps and end gates do not always retain the milled material within the broom assembly. In addition, some of these machines may trap material within the broom only to eject it onto the roadway behind the machine as the broom rotates. It would be desirable if a broom assembly could be provided for a sweeping machine with a collecting assembly that would more efficiently contain milled material within the broom enclosure and direct such material onto a discharge conveyor.